Wireless MEMS sensor and method of reading the same

Abstract

This document describes a wireless sensor comprising a MEMS resonator and an antenna directly matched thereto. Also a method of reading the wireless sensor is described. The method comprises illuminating the wireless sensor with electromagnetic energy at a first and second frequencies and receiving an intermodulation signal emitted by the wireless sensor in response to said electromagnetic energy at the first and second frequencies.

The invention claimed is: 
     
       1. A wireless sensor, comprising a MEMS resonator and an antenna directly matched thereto, the wireless sensor adapted to emit electromagnetic signal at an intermodulation frequency when illuminated by electromagnetic energy at first and second frequencies,
 wherein at least one of the first and second frequencies is swept in order to measure a MEMS parameter of the MEMS resonator, the MEMS parameter including one of: a mechanical quality factor, a mechanical resonance frequency or an electrical resonance frequency. 
 
     
     
       2. The wireless sensor of  claim 1 , wherein the sensor is comprised in a single silicon chip. 
     
     
       3. The wireless sensor of  claim 2 , wherein the sensor is a passive sensor and the single silicon chip does not include a power rectifier nor a power source. 
     
     
       4. The wireless sensor of  claim 1 , wherein the sensor comprises a logic circuit. 
     
     
       5. The wireless sensor of  claim 2 , wherein the sensor comprises a logic implemented by a CMOS circuit manufacture on said single silicon chip. 
     
     
       6. The wireless sensor of  claim 1 , wherein
 the MEMS resonator has three MEMS parameters: the mechanical quality factor, the mechanical resonance frequency, and the electrical resonance frequency; and 
 at least one of the three MEMS parameters is sensitive to a measured quantity. 
 
     
     
       7. The wireless sensor of  claim 6 , wherein the sensor is adapted to provide the intermodulation frequency in the frequency range from 100 kHz to 300 GHz. 
     
     
       8. A method of reading a wireless sensor including a MEMS resonator and an antenna directly matched thereto, the wireless sensor adapted to emit electromagnetic signal at an intermodulation frequency when illuminated by electromagnetic energy at two different frequencies, the method comprising:
 illuminating the wireless sensor with electromagnetic energy at a first and second frequencies; 
 sweeping at least one of the first and second frequencies; 
 receiving the intermodulation signal emitted by the wireless sensor in response to said electromagnetic energy at the first and second frequencies; and 
 
       measuring the mechanical quality factor of the MEMS resonator by sweeping the first frequency and keeping the second frequency fixed. 
     
     
       9. The method of  claim 8 , wherein the first and second frequencies are in the frequency range from 100 kHz to 300 GHz. 
     
     
       10. The method of  claim 8 , wherein the mechanical quality factor of the MEMS resonator is sensitive to a measured quantity, the measured quantity being at least one of temperature, strain, air pressure and humidity. 
     
     
       11. The method of  claim 10 , wherein the measured quantity is at least one of temperature, strain, air pressure and humidity. 
     
     
       12. The wireless sensor of  claim 6 , wherein the measured quantity is at least one of temperature, strain, air pressure and humidity. 
     
     
       13. A reader for reading a wireless sensor comprising a MEMS resonator and an antenna directly matched thereto, the wireless sensor adapted to emit electromagnetic signal at an intermodulation frequency when illuminated by electromagnetic energy at two different frequencies, the reader comprising:
 signal generators configured to generate first and second signals respectively at first and second frequencies, at least one of the signal generators being further configured to sweep the respective first or second frequency, wherein the first or second frequency is swept in order to measure a MEMS parameter of the MEMS resonator, the MEMS parameter including one of a mechanical quality factor, a mechanical resonance frequency or an electrical resonance frequency; and 
 antenna connected to the signal generators and configured to illuminate the wireless sensor with electromagnetic energy at the first and second frequencies and receive the electromagnetic signal emitted by the wireless sensor in response to said electromagnetic energy at the first and second frequencies. 
 
     
     
       14. A method of reading a wireless sensor including a MEMS resonator and an antenna directly matched thereto, the wireless sensor adapted to emit electromagnetic signal at an intermodulation frequency when illuminated by electromagnetic energy at two different frequencies, the method comprising:
 illuminating the wireless sensor with electromagnetic energy at a first and second frequencies; 
 sweeping at least one of the first and second frequencies; 
 receiving the intermodulation signal emitted by the wireless sensor in response to said electromagnetic energy at the first and second frequencies; and 
 measuring the mechanical resonance frequency of the MEMS resonator by sweeping the first frequency and keeping the second frequency fixed. 
 
     
     
       15. The method of  claim 14 , wherein the mechanical resonance frequency of the MEMS resonator is sensitive to a measured quantity, the measured quantity being at least one of temperature, strain, air pressure and humidity. 
     
     
       16. The method of  claim 15 , wherein the measured quantity is at least one of temperature, strain, air pressure and humidity. 
     
     
       17. A method of reading a wireless sensor including a MEMS resonator and an antenna directly matched thereto, the wireless sensor adapted to emit electromagnetic signal at an intermodulation frequency when illuminated by electromagnetic energy at two different frequencies, the method comprising:
 illuminating the wireless sensor with electromagnetic energy at a first and second frequencies; 
 sweeping at least one of the first and second frequencies; 
 receiving the intermodulation signal emitted by the wireless sensor in response to said electromagnetic energy at the first and second frequencies; and 
 measuring the electrical resonance frequency of the MEMS resonator by sweeping the first and second frequencies at a same rate. 
 
     
     
       18. The method of  claim 17 , wherein the electrical resonance frequency of the MEMS resonator is sensitive to a measured quantity, the measured quantity being at least one of temperature, strain, air pressure and humidity. 
     
     
       19. The method of  claim 18 , wherein the measured quantity is at least one of temperature, strain, air pressure and humidity.